In most categories, if you either solve a new problem that a lot of people have, or solve an old problem in a new and better way, you can sell a paid app today just as well as you could in 2008. In fact, the market is much bigger now. But, as with any maturing market, you’ll need to do more to get noticed since so many problems have already been solved so well.

If you're a developer trying to get traction on a current app, or you're thinking of entering the market with your own app, you need to read this.